313 relations: Abd al-Rahman al-Sufi, Abell 1835 IR1916, Accretion disk, Active galactic nucleus, Al-Andalus, Al-Biruni, Ancient Greek, Ancient Greek philosophy, Andromeda (constellation), Andromeda Galaxy, Angular diameter, Angular velocity, Anisotropy, Annual Review of Astronomy and Astrophysics, Antennae Galaxies, Aristotle, Astronomical Society of the Pacific, Astronomy & Astrophysics, Astronomy in the medieval Islamic world, Astrophysical jet, Astrophysics, Astrophysics and Space Science, Asymptotic giant branch, Atmosphere, Atom, Avempace, Barred lenticular galaxy, Barred spiral galaxy, Baryon, Big Bang, Black dwarf, Black hole, Blazar, Book of Fixed Stars, Brightest cluster galaxy, Brown dwarf, Bulge (astronomy), Bulletin of the American Astronomical Society, California Institute of Technology, Cambridge University Press, Canis Major Overdensity, Carbon dioxide, Carnegie Mellon University, Catalogue of Galaxies and Clusters of Galaxies, Center of mass, Centre for Astrophysics and Supercomputing, Cepheid variable, Chandra, Charles Messier, Chemical element, ..., Christopher Conselice, Cold dark matter, Coma Berenices, Comoving and proper distances, Compact star, Conjunction (astronomy), Constellation, Cornell University, Cosmic dust, Cosmos Redshift 7, CRC Press, Czech Academy of Sciences, Dark galaxy, Dark matter, Declination, Democritus, Density wave theory, Distance measures (cosmology), Doppler effect, Dwarf elliptical galaxy, Dwarf galaxy, Dwarf spheroidal galaxy, Dwarf spiral galaxy, Earth, Edwin Hubble, EGS-zs8-1, Electromagnetic spectrum, Ellipsoid, Elliptical galaxy, Emanuel Swedenborg, Ernst Öpik, Estonia, European Southern Observatory, European Space Agency, Expansion of the universe, Extinction (astronomy), Far-infrared astronomy, Ferdinand Magellan, Flocculent spiral galaxy, Fractal, Galactic Disc, Galactic orientation, Galactic plane, Galactic tide, Galactocentrism, Galaxy cluster, Galaxy filament, Galaxy formation and evolution, Galaxy group, Galaxy morphological classification, Galaxy rotation curve, Galileo Galilei, Gauss (unit), Geoffrey Chaucer, George Mason University, Globular cluster, GN-z11, Grand design spiral galaxy, Gravitational energy, Gravity, Great Debate (astronomy), Greek language, Greek mythology, H II region, Harlow Shapley, Harvard University Press, Harvard–Smithsonian Center for Astrophysics, Heber Doust Curtis, Helium, Hendrik C. van de Hulst, Hera, Heracles, Hertz, High-velocity cloud, Hubble Deep Field, Hubble sequence, Hubble Space Telescope, Hubble Ultra-Deep Field, Hubble's law, Hydrogen, Hydrogen line, Ibn al-Haytham, Ibn Qayyim al-Jawziyya, IC 1101, Illustris project, Immanuel Kant, Infrared, Infrared astronomy, Infrared Processing and Analysis Center, Institute of Astronomy, Cambridge, Institute of Physics, Interacting galaxy, Interferometry, Interstellar medium, IOK-1, Ion, Ionosphere, Irregular galaxy, Isotropy, Jacobus Kapteyn, Journal of the American Oriental Society, Journal of the Royal 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(temperature), Outer space, Outline of galaxies, Pan Books, Parallax, Paris Observatory, Parsec, Peculiar galaxy, Persian people, Physics Reports, Pinwheel (toy), Pisces–Cetus Supercluster Complex, Planet, Popular Astronomy (US magazine), Princeton University Press, Protogalaxy, Publications of the Astronomical Society of Australia, Publications of the Astronomical Society of the Pacific, Quasar, Radio astronomy, Radio galaxy, Radio telescope, Recombination (cosmology), Red dwarf, Redshift, Refraction, Relaxation (physics), Ring galaxy, Robert Julius Trumpler, Royal Astronomical Society, Sagittarius A*, Sagittarius Dwarf Spheroidal Galaxy, San Diego Supercomputer Center, Sand, Science (journal), Science Daily, Scientific American, Seyfert galaxy, Seyfert's Sextet, Simon Marius, Small Magellanic Cloud, SN 1885A, Solar mass, Solar System, Sombrero Galaxy, Sonoma State University, Space.com, Speed of light, Spiral galaxy, Springer Science+Business Media, Stanford Encyclopedia of 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'Abd al-Rahman al-Sufi (عبدالرحمن صوفی (December 7, 903 in Rey, Iran – May 25, 986 in Shiraz, Iran) was a Persian astronomer also known as 'Abd ar-Rahman as-Sufi, 'Abd al-Rahman Abu al-Husayn, 'Abdul Rahman Sufi, or 'Abdurrahman Sufi and, historically, in the West as Azophi and Azophi Arabus. The lunar crater Azophi and the minor planet 12621 Alsufi are named after him. Al-Sufi published his famous Book of Fixed Stars in 964, describing much of his work, both in textual descriptions and pictures. Al-Biruni reports that his work on the ecliptic was carried out in Shiraz. He lived at the Buyid court in Isfahan.
Abell 1835 IR1916 (also known as Abell 1835, Galaxy Abell 1835, Galaxy Abell 1835 IR1916, or simply The Abell) was a candidate for being the most distant galaxy ever observed, although that claim has not been verified by additional observations.
An accretion disk is a structure (often a circumstellar disk) formed by diffused material in orbital motion around a massive central body.
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion—and possibly all—of the electromagnetic spectrum, with characteristics indicating that the excess luminosity is not produced by stars.
Al-Andalus (الأنْدَلُس, trans.; al-Ándalus; al-Ândalus; al-Àndalus; Berber: Andalus), also known as Muslim Spain, Muslim Iberia, or Islamic Iberia, was a medieval Muslim territory and cultural domain occupying at its peak most of what are today Spain and Portugal.
Abū Rayḥān Muḥammad ibn Aḥmad Al-Bīrūnī (Chorasmian/ابوریحان بیرونی Abū Rayḥān Bērōnī; New Persian: Abū Rayḥān Bīrūnī) (973–1050), known as Al-Biruni (البيروني) in English, was an IranianD.J. Boilot, "Al-Biruni (Beruni), Abu'l Rayhan Muhammad b. Ahmad", in Encyclopaedia of Islam (Leiden), New Ed., vol.1:1236–1238.
The Ancient Greek language includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD.
Ancient Greek philosophy arose in the 6th century BC and continued throughout the Hellenistic period and the period in which Ancient Greece was part of the Roman Empire.
Andromeda is one of the 48 constellations listed by the 2nd-century Greco-Roman astronomer Ptolemy and remains one of the 88 modern constellations.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.
The angular diameter, angular size, apparent diameter, or apparent size is an angular measurement describing how large a sphere or circle appears from a given point of view.
In physics, the angular velocity of a particle is the rate at which it rotates around a chosen center point: that is, the time rate of change of its angular displacement relative to the origin.
Anisotropy, is the property of being directionally dependent, which implies different properties in different directions, as opposed to isotropy.
The Annual Review of Astronomy and Astrophysics is an annual peer reviewed scientific journal published by Annual Reviews.
The Antennae Galaxies, also known as NGC 4038/NGC 4039, are a pair of interacting galaxies in the constellation Corvus.
Aristotle (Ἀριστοτέλης Aristotélēs,; 384–322 BC) was an ancient Greek philosopher and scientist born in the city of Stagira, Chalkidiki, in the north of Classical Greece.
The Astronomical Society of the Pacific (ASP) is an American scientific and educational organization, founded in San Francisco on February 7, 1889.
Astronomy & Astrophysics is a peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics.
Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9th–13th centuries), and mostly written in the Arabic language.
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation.
Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space".
Astrophysics and Space Science is a bimonthly peer-reviewed scientific journal covering astronomy, astrophysics, and space science and astrophysical aspects of astrobiology.
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars.
An atmosphere is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
Avempace (– 1138) is the Latinate form of Ibn Bâjja (ابن باجه), full name Abû Bakr Muḥammad Ibn Yaḥyà ibn aṣ-Ṣâ’igh at-Tûjîbî Ibn Bâjja al-Tujibi (أبو بكر محمد بن يحيى بن الصائغ), was an Arab Andalusian polymath: his writings include works regarding astronomy, physics, and music, as well as philosophy, medicine, botany, and poetry.
A barred lenticular galaxy is a lenticular version of a barred spiral galaxy.
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars.
A baryon is a composite subatomic particle made up of three quarks (a triquark, as distinct from mesons, which are composed of one quark and one antiquark).
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
A black dwarf is a theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light.
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.
A blazar is a very compact quasar (quasi-stellar radio source) associated with a presumed supermassive black hole at the center of an active, giant elliptical galaxy.
The Book of Fixed Stars (كتاب صور الكواكب) is an astronomical text written by Abd al-Rahman al-Sufi (Azophi) around 964.
A brightest cluster galaxy (BCG) is defined as the brightest galaxy in a cluster of galaxies.
Brown dwarfs are substellar objects that occupy the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter, or approximately to about.
In astronomy, a bulge is a tightly packed group of stars within a larger formation.
Bulletin of the American Astronomical Society (BAAS; Bull. Am. Astron. Soc.) is the journal of record for the American Astronomical Society established in 1969.
The California Institute of Technology (abbreviated Caltech)The university itself only spells its short form as "Caltech"; other spellings such as.
Cambridge University Press (CUP) is the publishing business of the University of Cambridge.
The Canis Major Dwarf Galaxy (CMa Dwarf) or Canis Major Overdensity (CMa Overdensity) is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.
Carbon dioxide (chemical formula) is a colorless gas with a density about 60% higher than that of dry air.
Carnegie Mellon University (commonly known as CMU) is a private research university in Pittsburgh, Pennsylvania.
The Catalogue of Galaxies and of Clusters of Galaxies (pr CGCG) was compiled by Fritz Zwicky in 1961–68.
In physics, the center of mass of a distribution of mass in space is the unique point where the weighted relative position of the distributed mass sums to zero, or the point where if a force is applied it moves in the direction of the force without rotating.
The Centre for Astrophysics and Supercomputing (CAS) is a research centre located at the Swinburne University in Melbourne, Australia.
A Cepheid variable is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.
Chandra (चन्द्र, IAST: Candra, lit. "shining" or "moon")Graha Sutras By Ernst Wilhelm, Published by Kala Occult Publishers p.51 is a lunar deity and is also one of the nine planets (Navagraha) in Hinduism.
Charles Messier (26 June 1730 – 12 April 1817) was a French astronomer most notable for publishing an astronomical catalogue consisting of nebulae and star clusters that came to be known as the 110 "Messier objects".
A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).
Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.
The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.
Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.
Christmas traditions vary from country to country.
Christopher Conselice is an American Professor of Astrophysics at the University of Nottingham.
In cosmology and physics, cold dark matter (CDM) is a hypothetical form of dark matter whose particles moved slowly compared to the speed of light (the cold in CDM) since the universe was approximately one year old (a time when the cosmic particle horizon contained the mass of one typical galaxy); and interact very weakly with ordinary matter and electromagnetic radiation (the dark in CDM).
Coma Berenices is an ancient asterism in the northern sky which has been defined as one of the 88 modern constellations.
In standard cosmology, comoving distance and proper distance are two closely related distance measures used by cosmologists to define distances between objects.
In astronomy, the term "compact star" (or "compact object") refers collectively to white dwarfs, neutron stars, and black holes.
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
Cornell University is a private and statutory Ivy League research university located in Ithaca, New York.
Cosmic dust, also called extraterrestrial dust or space dust, is dust which exists in outer space, as well as all over planet Earth.
Cosmos Redshift 7 (also known as COSMOS Redshift 7, Galaxy Cosmos Redshift 7, Galaxy CR7 or CR7) is a high-redshift Lyman-alpha emitter galaxy (meaning CR7 is one of the oldest, most distant galaxies), in the constellation Sextans, about 12.9 billion light travel distance years from Earth, reported to contain the first stars (first generation; Population III)—formed soon after the Big Bang during the reionisation epoch (redshift, z ∼ 6−7), when the Universe was about 800 million years old—to have provided the chemical elements (like oxygen, nitrogen, carbon, calcium and iron) needed for the later formation of planets and life as it is known.
The CRC Press, LLC is a publishing group based in the United States that specializes in producing technical books.
The Czech Academy of Sciences (abbr. CAS, Akademie věd České republiky, abbr. AV ČR) was established in 1992 by the Czech National Council as the Czech successor of the former Czechoslovak Academy of Sciences and its tradition goes back to the Royal Bohemian Society of Sciences (founded in 1784) and the Emperor Franz Joseph Czech Academy for Sciences, Literature and Arts (founded in 1890).The Academy is the leading non-university public research institution in the Czech Republic.
A dark galaxy is a hypothesized galaxy with no, or very few, stars.
Dark matter is a theorized form of matter that is thought to account for approximately 80% of the matter in the universe, and about a quarter of its total energy density.
In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle.
Democritus (Δημόκριτος, Dēmókritos, meaning "chosen of the people") was an Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe.
Density wave theory or the Lin-Shu density wave theory is a theory proposed by C.C. Lin and Frank Shu in the mid-1960s to explain the spiral arm structure of spiral galaxies.
Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.
The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source.
Dwarf elliptical galaxies, or dEs, are elliptical galaxies that are smaller than ordinary elliptical galaxies.
A dwarf galaxy is a small galaxy composed of about 100 million up to several billion stars, a small number compared to the Milky Way's 200–400 billion stars.
A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population.
A dwarf spiral galaxy is the dwarf version of a spiral galaxy.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer.
EGS-zs8-1 is a high-redshift Lyman-break galaxy found at the northern constellation of Boötes.
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation.
An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless image.
Emanuel Swedenborg ((born Emanuel Swedberg; 29 January 1688 – 29 March 1772) was a Swedish Lutheran theologian, scientist, philosopher, revelator and mystic who inspired Swedenborgianism. He is best known for his book on the afterlife, Heaven and Hell (1758). Swedenborg had a prolific career as an inventor and scientist. In 1741, at 53, he entered into a spiritual phase in which he began to experience dreams and visions, beginning on Easter Weekend, on 6 April 1744. It culminated in a 'spiritual awakening' in which he received a revelation that he was appointed by the Lord Jesus Christ to write The Heavenly Doctrine to reform Christianity. According to The Heavenly Doctrine, the Lord had opened Swedenborg's spiritual eyes so that from then on, he could freely visit heaven and hell and talk with angels, demons and other spirits and the Last Judgment had already occurred the year before, in 1757. For the last 28 years of his life, Swedenborg wrote 18 published theological works—and several more that were unpublished. He termed himself a "Servant of the Lord Jesus Christ" in True Christian Religion, which he published himself. Some followers of The Heavenly Doctrine believe that of his theological works, only those that were published by Swedenborg himself are fully divinely inspired.
Ernst Julius Öpik (– 10 September 1985) was an Estonian astronomer and astrophysicist who spent the second half of his career (1948–1981) at the Armagh Observatory in Northern Ireland.
Estonia (Eesti), officially the Republic of Estonia (Eesti Vabariik), is a sovereign state in Northern Europe.
The European Southern Observatory (ESO) is a 15-nation intergovernmental research organization for ground-based astronomy.
The European Space Agency (ESA; Agence spatiale européenne, ASE; Europäische Weltraumorganisation) is an intergovernmental organisation of 22 member states dedicated to the exploration of space.
The expansion of the universe is the increase of the distance between two distant parts of the universe with time.
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer.
Far-infrared astronomy is the branch of astronomy and astrophysics that deals with objects visible in far-infrared radiation (extending from 30 µm towards submillimeter wavelengths around 450 µm).
Ferdinand Magellan (or; Fernão de Magalhães,; Fernando de Magallanes,; c. 1480 – 27 April 1521) was a Portuguese explorer who organised the Spanish expedition to the East Indies from 1519 to 1522, resulting in the first circumnavigation of the Earth, completed by Juan Sebastián Elcano.
A flocculent spiral galaxy is a type of spiral galaxy.
In mathematics, a fractal is an abstract object used to describe and simulate naturally occurring objects.
The Galactic Disc is a component of disc galaxies, such as spiral galaxies and lenticular galaxies.
Galactic clusters are gravitationally bound large-scale structures of multiple galaxies.
The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies.
A galactic tide is a tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way.
In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earths Solar System, is at or near the center of the Universe.
A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity with typical masses ranging from 1014–1015 solar masses.
The distribution reveals fine, filamentary structures.
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies.
A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxies larger than groups that are first-order clustering are called galaxy clusters.
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance.
The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre.
Galileo Galilei (15 February 1564Drake (1978, p. 1). The date of Galileo's birth is given according to the Julian calendar, which was then in force throughout Christendom. In 1582 it was replaced in Italy and several other Catholic countries with the Gregorian calendar. Unless otherwise indicated, dates in this article are given according to the Gregorian calendar. – 8 January 1642) was an Italian polymath.
The gauss, abbreviated as G or Gs, is the cgs unit of measurement of magnetic flux density (or "magnetic induction") (B).
Geoffrey Chaucer (c. 1343 – 25 October 1400), known as the Father of English literature, is widely considered the greatest English poet of the Middle Ages.
George Mason University (GMU, Mason, or George Mason) is a public research university in Fairfax County, Virginia.
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite.
GN-z11 is a high-redshift galaxy found in the constellation Ursa Major.
A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features.
Gravitational energy is the potential energy a body with mass has in relation to another massive object due to gravity.
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another.
The Great Debate, also called the Shapley–Curtis Debate, was held on 26 April 1920 at the Smithsonian Museum of Natural History, between the astronomers Harlow Shapley and Heber Curtis.
Greek (Modern Greek: ελληνικά, elliniká, "Greek", ελληνική γλώσσα, ellinikí glóssa, "Greek language") is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean and the Black Sea.
Greek mythology is the body of myths and teachings that belong to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices.
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized.
Harlow Shapley (November 2, 1885 – October 20, 1972) was a 20th-century American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal.
Harvard University Press (HUP) is a publishing house established on January 13, 1913, as a division of Harvard University, and focused on academic publishing.
The Harvard–Smithsonian Center for Astrophysics (CfA) is a research institute which carries out a broad program of research in astronomy, astrophysics, earth and space sciences, and science education.
Heber Doust Curtis (June 27, 1872 – January 9, 1942) was an American astronomer.
Helium (from lit) is a chemical element with symbol He and atomic number 2.
Hendrik Christoffel "Henk" van de Hulst (19 November 1918 – 31 July 2000) was a Dutch astronomer and mathematician.
Hera (Ἥρᾱ, Hērā; Ἥρη, Hērē in Ionic and Homeric Greek) is the goddess of women, marriage, family, and childbirth in Ancient Greek religion and myth, one of the Twelve Olympians and the sister-wife of Zeus.
Heracles (Ἡρακλῆς, Hēraklês, Glory/Pride of Hēra, "Hera"), born Alcaeus (Ἀλκαῖος, Alkaios) or Alcides (Ἀλκείδης, Alkeidēs), was a divine hero in Greek mythology, the son of Zeus and Alcmene, foster son of AmphitryonBy his adoptive descent through Amphitryon, Heracles receives the epithet Alcides, as "of the line of Alcaeus", father of Amphitryon.
The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second.
High-velocity clouds (HVCs) are large collections of gas found throughout the galactic halo of the Milky Way.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope.
The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926.
The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.
The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies.
Hubble's law is the name for the observation in physical cosmology that.
Hydrogen is a chemical element with symbol H and atomic number 1.
The hydrogen line, 21-centimeter line or H I line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms.
Hasan Ibn al-Haytham (Latinized Alhazen; full name أبو علي، الحسن بن الحسن بن الهيثم) was an Arab mathematician, astronomer, and physicist of the Islamic Golden Age.
Shams al-Dīn Abū ʿAbd Allāh Muḥammad ibn Abī Bakr ibn Ayyūb al-Zurʿī l-Dimashqī l-Ḥanbalī (1292–1350 CE / 691 AH–751 AH), commonly known as Ibn Qayyim al-Jawziyya ("The son of the principal of Jawziyyah") or Ibn al-Qayyim ("Son of the principal"; ابن قيم الجوزية) for short, or reverentially as Imam Ibn al-Qayyim in Sunni tradition, was an important medieval Islamic jurisconsult, theologian, and spiritual writer.
IC 1101 is a supergiant elliptical galaxy at the center of the Abell 2029 galaxy cluster, approximately 320 megaparsecs (1.04 billion light-years) from Earth.
The Illustris project is an ongoing series of astrophysical simulations run by an international collaboration of scientists.
Immanuel Kant (22 April 1724 – 12 February 1804) was a German philosopher who is a central figure in modern philosophy.
Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.
Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared (IR) radiation.
The Infrared Processing and Analysis Center (IPAC) provides science operations, data management, data archives and community support for astronomy and planetary science missions.
The Institute of Astronomy (IoA) is the largest of the three astronomy departments in the University of Cambridge, and one of the largest astronomy sites in the UK.
The Institute of Physics (IOP) is a scientific charity that works to advance physics education, research and application.
Interacting galaxies (colliding galaxies) are galaxies whose gravitational fields result in a disturbance of one another.
Interferometry is a family of techniques in which waves, usually electromagnetic waves, are superimposed causing the phenomenon of interference in order to extract information.
In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.
IOK-1 is a distant galaxy in the constellation Coma Berenices.
An ion is an atom or molecule that has a non-zero net electrical charge (its total number of electrons is not equal to its total number of protons).
The ionosphere is the ionized part of Earth's upper atmosphere, from about to altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere.
An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.
Isotropy is uniformity in all orientations; it is derived from the Greek isos (ἴσος, "equal") and tropos (τρόπος, "way").
Prof Jacobus Cornelius Kapteyn FRS FRSE LLD (19 January 1851 – 18 June 1922) was a Dutch astronomer.
The Journal of the American Oriental Society is a quarterly academic journal published by the American Oriental Society since 1843.
The Journal of the Royal Astronomical Society of Canada is a bimonthly peer-reviewed scientific journal published by the Royal Astronomical Society of Canada since 1907.
Kessinger Publishing LLC is an American print on demand publishing company located in Whitefish, Montana that specializes in rare, out of print books.
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
The Kyklos (κύκλος,, "cycle") is a term used by some classical Greek authors to describe what they saw as the political cycle of governments in a society.
The Laniakea Supercluster (Laniakea; also called Local Supercluster or Local SCl or sometimes Lenakaeia) is the galaxy supercluster that is home to the Milky Way and approximately 100,000 other nearby galaxies.
The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way.
A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes.
Life is a characteristic that distinguishes physical entities that do have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate.
The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.
The following is a list of notable galaxies.
This is a list of known galaxies within 3.59 megaparsecs (11.7 million light-years) of the Solar System, in ascending order of distance.
The Local Group is the galaxy group that includes the Milky Way.
A logarithmic spiral, equiangular spiral or growth spiral is a self-similar spiral curve which often appears in nature.
A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission.
Luminous infrared galaxies or LIRGs are galaxies with luminosities, the measurement of brightness, above.
The Magellanic Clouds (or Nubeculae Magellani) are two irregular dwarf galaxies visible in the Southern Celestial Hemisphere; they are members of the Local Group and are orbiting the Milky Way galaxy.
A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.
In astronomy, magnitude is a logarithmic measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths.
Messier 109 (also known as NGC 3992) is a barred spiral galaxy exhibiting a weak inner ring structure around the central bar approximately It is also by far the most distant object in the Messier Catalog, followed by M91 away in the constellation Ursa Major.
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away, in the constellation Ursa Major.
Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa Major.
The Messier objects are a set of 110 astronomical objects, of which 103 were included in lists published by French astronomer Charles Messier in 1771 and 1781.
In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium.
Metre per second (American English: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.
NGC 4676, or the Mice Galaxies, are two spiral galaxies in the constellation Coma Berenices.
Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between and.
The Milky Way is the galaxy that contains our Solar System.
The Millennium Run, or Millennium Simulation (referring to its size) is a computer N-body simulation used to investigate how the distribution of matter in the Universe has evolved over time, in particular, how the observed population of galaxies was formed.
The MIT Press is a university press affiliated with the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts (United States).
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H2).
Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
The Morphological Catalogue of Galaxies (MCG) or Morfologiceskij Katalog Galaktik, is a Russian catalogue of 30,642 galaxies compiled by Boris Vorontsov-Velyaminov and V. P. Arkhipova.
The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States.
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical instrument, such as a telescope or microscope.
The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.
The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization.
The National Radio Astronomy Observatory (NRAO) is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy.
Nature is a British multidisciplinary scientific journal, first published on 4 November 1869.
A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases.
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems).
Neoplatonism is a term used to designate a strand of Platonic philosophy that began with Plotinus in the third century AD against the background of Hellenistic philosophy and religion.
A neutron star is the collapsed core of a large star which before collapse had a total of between 10 and 29 solar masses.
The New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC) is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888.
New Scientist, first published on 22 November 1956, is a weekly, English-language magazine that covers all aspects of science and technology.
NGC 4414 is an unbarred spiral galaxy about 62 million light-years away in the constellation Coma Berenices.
New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.
New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.
A nova (plural novae or novas) or classical nova (CN, plural CNe) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or many months.
The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion.
Olympiodorus the Younger (Ὀλυμπιόδωρος ὁ Νεώτερος; c. 495 – 570) was a Neoplatonist philosopher, astrologer and teacher who lived in the early years of the Byzantine Empire, after Justinian's Decree of 529 AD which closed Plato's Academy in Athens and other pagan schools.
The Online Etymology Dictionary is a free online dictionary written and compiled by Douglas Harper that describes the origins of English-language words.
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.
An optical telescope is a telescope that gathers and focuses light, mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct view, or to make a photograph, or to collect data through electronic image sensors.
Most ordinary human activity takes place at temperatures of this order of magnitude.
Outer space, or just space, is the expanse that exists beyond the Earth and between celestial bodies.
The following outline is provided as an overview of and topical guide to galaxies: Galaxies – gravitationally bound systems of stars, stellar remnants, interstellar gas, dust, and dark matter.
Pan Books is a publishing imprint that first became active in the 1940s and is now part of the British-based Macmillan Publishers, owned by the Georg von Holtzbrinck Publishing Group of Germany.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.
The Paris Observatory (Observatoire de Paris or Observatoire de Paris-Meudon), a research institution of PSL Research University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world.
The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.
A peculiar galaxy is a galaxy of unusual size, shape, or composition.
The Persians--> are an Iranian ethnic group that make up over half the population of Iran.
Physics Reports is a peer-reviewed scientific journal, a review section of Physics Letters that has been published by Elsevier since 1971.
A pinwheel is a simple child's toy made of a wheel of paper or plastic curls attached at its axle to a stick by a pin.
The Pisces–Cetus Supercluster Complex is a galaxy filament.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
Popular Astronomy is an American magazine published by John August Media, LLC and hosted at TechnicaCuriosa.com for amateur astronomers.
Princeton University Press is an independent publisher with close connections to Princeton University.
In physical cosmology, a protogalaxy, which could also be called a "primeval galaxy", is a cloud of gas which is forming into a galaxy.
Publications of the Astronomical Society of Australia is a peer-reviewed scientific journal covering all aspects of astrophysics and astronomy.
Publications of the Astronomical Society of the Pacific (often abbreviated as PASP in references and literature) is a monthly peer-reviewed scientific journal managed by the Astronomical Society of the Pacific.
A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies.
Radio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths, with luminosities up to 1039 W between 10 MHz and 100 GHz.
A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy.
In cosmology, recombination refers to the epoch at which charged electrons and protons first became bound to form electrically neutral hydrogen atoms.
A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.
In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.
Refraction is the change in direction of wave propagation due to a change in its transmission medium.
In the physical sciences, relaxation usually means the return of a perturbed system into equilibrium.
A ring galaxy is a galaxy with a circle-like appearance.
Robert Julius Trumpler (until 1915 Robert Trümpler, born October 2, 1886 in Zürich, Switzerland; died September 10, 1956 in Berkeley, United States) was a Swiss-American astronomer.
The Royal Astronomical Society (RAS) is a learned society that began as the Astronomical Society of London in 1820 to support astronomical research (mainly carried on at the time by 'gentleman astronomers' rather than professionals).
Sagittarius A* (pronounced "Sagittarius A-star", standard abbreviation Sgr A*) is a bright and very compact astronomical radio source at the center of the Milky Way, near the border of the constellations Sagittarius and Scorpius.
The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy (Sgr dE or Sag DEG), is an elliptical loop-shaped satellite galaxy of the Milky Way.
The San Diego Supercomputer Center (SDSC) is an organized research unit of the University of California San Diego (UCSD).
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.
Science, also widely referred to as Science Magazine, is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals.
Science Daily is an American website that aggregates press releases and publishes lightly edited press releases (a practice called churnalism) about science, similar to Phys.org and EurekAlert!.
Scientific American (informally abbreviated SciAm) is an American popular science magazine.
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars.
Seyfert's Sextet is a group of galaxies about 190 million light-years away in the constellation Serpens.
Simon Marius (Latinized from German Simon Mayr; January 20, 1573 – January 5, 1625) was a German astronomer.
The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way.
The solar mass is a standard unit of mass in astronomy, equal to approximately.
The Solar SystemCapitalization of the name varies.
The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a spiral galaxy in the constellation Virgo located from Earth.
Sonoma State University (SSU, Sonoma State, and Sonoma) is a public comprehensive university, part of the 23-campus California State University (CSU) system.
Space.com is a space and astronomy news website.
The speed of light in vacuum, commonly denoted, is a universal physical constant important in many areas of physics.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.
Springer Science+Business Media or Springer, part of Springer Nature since 2015, is a global publishing company that publishes books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing.
The Stanford Encyclopedia of Philosophy (SEP) combines an online encyclopedia of philosophy with peer-reviewed publication of original papers in philosophy, freely accessible to Internet users.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.
Star clusters are groups of stars.
Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars.
A starburst galaxy is a galaxy undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies.
A starburst is an astrophysical process that involves star formation occurring at a rate that is large compared to the rate that is typically observed.
Various methods and tools are involved in stellar age estimation, an attempt to identify within reasonable degrees of confidence what the age of a star is.
Stellar evolution is the process by which a star changes over the course of time.
During 1944, Walter Baade categorized groups of stars within the Milky Way into bluer stars associated with the spiral arms and the general position of yellow stars near the central galactic bulge or within globular star clusters.
In physical cosmology, structure formation is the formation of galaxies, galaxy clusters and larger structures from small early density fluctuations.
In Aristotelian physics and Greek astronomy, the sublunary sphere is the region of the geocentric cosmos below the Moon, consisting of the four classical elements: earth, water, air, and fire.
The Sun is the star at the center of the Solar System.
A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos.
A supermassive black hole (SMBH or SBH) is the largest type of black hole, on the order of hundreds of thousands to billions of solar masses, and is found in the centre of almost all currently known massive galaxies.
A supernova (plural: supernovae or supernovas, abbreviations: SN and SNe) is a transient astronomical event that occurs during the last stellar evolutionary stages of a star's life, either a massive star or a white dwarf, whose destruction is marked by one final, titanic explosion.
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova.
Swinburne University of Technology (often simply called Swinburne) is an Australian public university based in Melbourne, Victoria.
The tesla (symbol T) is a derived unit of magnetic flux density (informally, magnetic field strength) in the International System of Units.
The Astronomical Journal (often abbreviated AJ in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society and currently published by IOP Publishing.
The Astrophysical Journal, often abbreviated ApJ (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler.
The House of Fame (Hous of Fame in the original spelling) is a Middle English poem by Geoffrey Chaucer, probably written between 1379 and 1380, making it one of his earlier works.
The New York Times (sometimes abbreviated as The NYT or The Times) is an American newspaper based in New York City with worldwide influence and readership.
Thomas Wright (22 September 171125 February 1786) was an English astronomer, mathematician, instrument maker, architect and garden designer.
The tidal force is an apparent force that stretches a body towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for the diverse phenomena, including tides, tidal locking, breaking apart of celestial bodies and formation of ring systems within Roche limit, and in extreme cases, spaghettification of objects.
Timeline of galaxies, clusters of galaxies, and large-scale structure of the universe.
The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum.
UDFj-39546284 is the designation given to a stellar structure reported on January 27, 2011, as light from the oldest object detected through infrared observation within the Hubble Space Telescope.
An ultra diffuse galaxy (UDG) is an extremely low luminosity galaxy, the first example of which was discovered in the nearby Virgo Cluster by Allan Sandage and Bruno Binggeli in 1984.
Ultraviolet astronomy is the observation of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma ray astronomy.
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
The University of Alabama (Alabama or UA) is a public research university located in Tuscaloosa, Alabama, United States, and the flagship of the University of Alabama System.
The University of Birmingham (informally Birmingham University) is a public research university located in Edgbaston, Birmingham, United Kingdom.
The University of California (UC) is a public university system in the US state of California.
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public research university in Berkeley, California.
The University of Cambridge (informally Cambridge University)The corporate title of the university is The Chancellor, Masters, and Scholars of the University of Cambridge.
The University of Leicester is a public research university based in Leicester, England.
The University of Maryland, College Park (commonly referred to as the University of Maryland, UMD, or simply Maryland) is a public research university located in the city of College Park in Prince George's County, Maryland, approximately from the northeast border of Washington, D.C. Founded in 1856, the university is the flagship institution of the University System of Maryland.
The University of Michigan (UM, U-M, U of M, or UMich), often simply referred to as Michigan, is a public research university in Ann Arbor, Michigan.
The University of Nottingham is a public research university in Nottingham, United Kingdom.
The University of St Andrews (informally known as St Andrews University or simply St Andrews; abbreviated as St And, from the Latin Sancti Andreae, in post-nominals) is a British public research university in St Andrews, Fife, Scotland.
The University of Toronto (U of T, UToronto, or Toronto) is a public research university in Toronto, Ontario, Canada on the grounds that surround Queen's Park.
The Uppsala General Catalogue of Galaxies (UGC) is a catalogue of 12,921 galaxies visible from the northern hemisphere.
Vera Florence Cooper Rubin (July 23, 1928 – December 25, 2016) was an American astronomer who pioneered work on galaxy rotation rates.
Vesto Melvin Slipher (November 11, 1875 – November 8, 1969) was an American astronomer who performed the first measurements of radial velocities for galaxies, providing the empirical basis for the expansion of the universe.
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo.
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which in turn contains the Milky Way and Andromeda galaxies.
In mechanics, the virial theorem provides a general equation that relates the average over time of the total kinetic energy, \left\langle T \right\rangle, of a stable system consisting of N particles, bound by potential forces, with that of the total potential energy, \left\langle V_\text \right\rangle, where angle brackets represent the average over time of the enclosed quantity.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
Visible-light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light (optical telescopes).
Cosmic voids are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies.
Warm dark matter (WDM) is a hypothesized form of dark matter that has properties intermediate between those of hot dark matter and cold dark matter, causing structure formation to occur bottom-up from above their free-streaming scale, and top-down below their free streaming scale.
The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus.
A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter.
The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP), was a spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic microwave background (CMB) – the radiant heat remaining from the Big Bang.
Frederick William Herschel, (Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer, composer and brother of fellow astronomer Caroline Herschel, with whom he worked.
William Parsons, 3rd Earl of Rosse HFRSE (17 June 1800 – 31 October 1867) was an Anglo-Irish astronomer who had several telescopes built.
X-rays make up X-radiation, a form of electromagnetic radiation.
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects.
Zeus (Ζεύς, Zeús) is the sky and thunder god in ancient Greek religion, who rules as king of the gods of Mount Olympus.
The Zone of Avoidance (ZOA) is the area of the sky that is obscured by the Milky Way.
2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.
2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.
Colonization of other galaxies, Galactic magnetic field, Galactic magnetic fields, Galactic nuclei, Galaxial center, Galaxies, Galaxy nucleus, Galixies, Gallaxy, Island universe, List of hypothetical galaxies.